Much activity has been devoted to avoiding the necessity of using on-floor conduits for conveying electrical power and communication lines to floor locations which were not within the original architectural and electrical planning of a facility, such as a multi-floor concrete building. On-floor conduits are unsightly and may also pose a safety hazard to persons working in such an area.
One technique for avoiding the use of on-floor conduits involves the drilling of a hole through the concrete floor at a desired location and the routing of power or communication lines beneath the floor and then up through the hole. Transition apparatus known as “poke-throughs” have been developed for use in such interfloor holes. Poke-throughs are subject to electrical and fire safety considerations. Among these considerations are two fire-related requirements. First, the poke-through cannot function as a chimney or fire-advancing flue in the event of a fire on the lower floor. Second, the poke-through cannot function as a floor-to-floor heat conduction path.
These safety requirements have largely been met through the use of intumescent material. For example, U.S. Pat. Nos. 5,003,127 and 5,107,072 disclose a poke-through assembly wherein a sheet of intumescent material is wired in place about a housing, and expands to fill and to block the interfloor hole in the event of fire. Furthermore, thermally insulating materials have been interposed between metallic (and therefore heat conductive) portions of the poke-through devices. Thus, poke-through devices have come into common use.
With greater use of poke-through devices, there is interest in making their manufacturing economical, their installation easier and faster, and their retention more positive. The United States Patent of James H. Whitehead, entitled “Poke-Through Electrical Connection Assembly Retainer,” U.S. Pat. No. 5,641,940, presents a solution to the problems of rapid installation, positive retention, and economical manufacturing. The '940 patent discloses a self-anchoring poke-through electrical connection assembly retainer, as well as a pre-formed intumescent material structure which is easy to apply during the manufacturing process.
However, problems still remain with the use of poke-through devices. One such problem involves ensuring that the intumescent material expands to completely fill and maintain a filled state long enough for the unit to meet applicable fire safety standards. Retaining the intumescent material in the poke-through under fire conditions has also proved challenging.
Accordingly, it would be desirable to provide a poke-through device that under fire conditions retains the intumescent material and permits the intumescent material to completely fill the poke-through.